Effect of Baghdadite Substitution on the Physicochemical Properties of Brushite Cements

Abstract

Brushite cements have been clinically used for irregular bone defect filling applications, and various strategies have been previously reported to modify and improve their physicochemical properties such as strength and injectability. However, strategies to address other limitations of brushite cements such as low radiopacity or acidity without negatively impacting mechanical strength have not yet been reported. In this study, we report the effect of substituting the beta-tricalcium phosphate reactant in brushite cement with baghdadite (Ca3ZrSi2O9), a bioactive zirconium-doped calcium silicate ceramic, at various concentrations (0, 5, 10, 20, 30, 50, and 100 wt%) on the properties of the final brushite cement product. X-ray diffraction profiles indicate the dissolution of baghdadite during the cement reaction, without affecting the crystal structure of the precipitated brushite. EDX analysis shows that calcium is homogeneously distributed within the cement matrix, while zirconium and silicon form cluster-like aggregates with sizes ranging from few microns to more than 50 µm. X-ray images and µ-CT analysis indicate enhanced radiopacity with increased incorporation of baghdadite into brushite cement, with nearly a doubling of the aluminium equivalent thickness at 50 wt% baghdadite substitution. At the same time, compressive strength of brushite cement increased from 12.9 ± 3.1 MPa to 21.1 ± 4.1 MPa with 10 wt% baghdadite substitution. Culture medium conditioned with powdered brushite cement approached closer to physiological pH values when the cement is incorporated with increasing amounts of baghdadite (pH = 6.47 for pure brushite, pH = 7.02 for brushite with 20 wt% baghdadite substitution). Baghdadite substitution also influenced the ionic content in the culture medium, and subsequently affected the proliferative activity of primary human osteoblasts in vitro. This study indicates that baghdadite is a beneficial additive to enhance the radiopacity, mechanical performance and cytocompatibility of brushite cements.

Baghdadite Ceramics Prevent Senescence in Human Osteoblasts and Promote Bone Regeneration in Aged Rats

“…First is the ability of Baghdadite to maintain a physical pH value of 7.3 in an extracellular solution . Extracellular pH plays a key role in the initiation of cellular senescence, and the maintenance of physiological pH conditions by Baghdadite might be able to correct the aged tissue-fostered inflammatory and acidic environment that promotes dysfunctional mitochondria and cellular senescence. , Second, the profile of ions (e.g., calcium and silicon) released by the Baghdadite material into the surrounding environment is distinct from that of HA/TCP. , Different ion conditions in the extracellular microenvironment can lead to significant changes in the ion channels present in the cellular membrane, which are implicated in modulating cellular senescence. , A recent study showed that there are regenerative and protective effects of ion extracts from calcium silicate on senescent fibroblasts induced by high glucose . It would be of great interest to gain further insight into how the soluble chemical environment, including ions and pH, modulate mitochondrial function and cellular senescence and ultimately contribute to tissue regeneration in the elderly.…”

“…A recent study showed that the microenvironment around oligodendrocyte progenitor cells stiffens with age and softening their substrate restores the function of these aged progenitor cells . The bone extracellular matrix structure and chemical composition are altered during the ageing process, , with a steady and significant decrease in bone mechanical properties and density. − In addition, other factors in the bone microenvironment also change with aging, including the age-related metabolic acidosis that plays an important role in the pathogenesis of the degenerative diseases of aging and loss of bone tissue. , We have developed a novel bioactive ceramic (Baghdadite, Ca 3 ZrSi 2 O 9 ) with improved mechanical properties, excellent biocompatibility, and bone regenerative capacity, in comparison to the clinically used bone graft substitute, hydroxyapatite (HA)/β-tricalcium phosphate (β-TCP). − Baghdadite also holds a unique ability to maintain simulated body fluid at a physiological pH of 7.3–7.5 . In this study, we hypothesized that Baghdadite scaffolds will foster an anti-senescent microenvironment to modulate the functionally compromised senescent bone cells and restore the in vivo impaired bone repair and regenerative capacity in old rats.…”

Rapid Fabrication of MgNH4PO4·H2O/SrHPO4 Porous Composite Scaffolds with Improved Radiopacity via 3D Printing Process

“…Commonly, bone repair scaffolds are required to possess high radiopacity for noninvasively tracking and imaging the filling effect in clinical operations, in vivo degradation, and new bone growth by X-ray-based techniques, such as fluoroscopy, computer tomography, and radiography [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. However, the intrinsic radiopacity of bone repair scaffolds is usually insufficient, and it is difficult to distinguish them from natural bone tissues.…”

“…However, the intrinsic radiopacity of bone repair scaffolds is usually insufficient, and it is difficult to distinguish them from natural bone tissues. For enhancing their radiopacity, X-ray contrast agents such as Ba-based [ 22 , 23 ], Zr-based [ 24 , 25 , 26 ], Bi-based [ 27 , 28 , 29 ], and Sr-based [ 30 , 31 , 32 ] compounds are added into them to construct the composite scaffolds. Although BaSO 4 and ZrO 2 are widely used in poly (methyl methacrylate) (PMMA) bone cements as the radiopacifier, there are potential physical, mechanical, and biological risks if the particles are released from the scaffolds as they are unabsorbable in the physiological environment [ 22 , 24 , 27 ].…”

Setting Characteristics and High Compressive Strength of an Anti-washout, Injectable Calcium Phosphate Cement Combined with Thermosensitive Hydrogel

“…CPC always consists of two phases, -solid particles and liquid, which, upon mixture with each other, form a moldable paste to fill the complex bone defect site and then undergo a hydration reaction, resulting in a strong material–bone interface [ 2 , 3 ]. The final cement product is hydroxyapatite (HA) or brushite phase, which resembles the inorganic components of human bone and thus provides a high level of biocompatibility and osteoconductivity [ 4 , 5 , 6 , 7 ].…”